JP7318450B2 - steering device - Google Patents

Description

The present invention relates to a steering device for independently steering steered wheels of a vehicle.

Conventional steering systems for automobiles do not have a mechanism that mechanically connects the steering wheel and the steered wheels or a mechanism that mechanically transmits torque between the steering wheel and the steered wheels. There are so-called steer-by-wire systems that steer the steerable wheels. Further, regarding the steer-by-wire system, there is a system in which the left and right steerable wheels are connected by a mechanical link, and a system in which the left and right steerable wheels are connected without a mechanical link between the left and right steerable wheels as described in Patent Document 1. A left and right independent rolling system has been proposed in which each steered wheel is steered by separate motors.

JP 2018-58484 A

However, when the steered wheels are steered independently using a motor as a drive source, the output torque of the motor is increased by a reduction gear to steer the steered wheels. Depending on the situation, etc., a so-called reverse input, in which torque is transmitted from the steered wheels to the reduction gear, occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a steering device that protects a speed reducer against reverse input from steered wheels.

In order to achieve the above object, a steering device, which is one aspect of the present invention, includes a motor that generates driving force for independently steering steered wheels, and a speed reducer that is connected to a rotating shaft of the motor. and a brake that suppresses transmission of torque between the motor and the speed reducer.

ADVANTAGE OF THE INVENTION According to this invention, even when there exists reverse input, the steering apparatus which can avoid damage to a reduction gear by suppressing rotation of a motor with a brake can be provided.

It is a figure which shows the steering apparatus which concerns on embodiment, a suspension mechanism, and a steered wheel. It is a sectional view showing a steering device concerning an embodiment. It is a block diagram showing a functional configuration of a brake control unit according to the embodiment. It is a sectional view showing other examples of a steering device.

EMBODIMENT OF THE INVENTION Below, embodiment of the steering apparatus which concerns on this invention is described, referring drawings. It should be noted that the numerical values, shapes, materials, components, positional relationships of components, connection states, steps, order of steps, etc. shown in the following embodiments are examples, and are not intended to limit the present invention. In the following, multiple inventions may be described as one embodiment, but constituent elements not described in a claim shall be explained as optional constituent elements with respect to the claimed invention. ing. In addition, the drawings are schematic diagrams in which emphasis, omissions, and ratios are appropriately adjusted in order to explain the present invention, and may differ from actual shapes, positional relationships, and ratios.

FIG. 1 is a diagram showing steered wheels and a suspension. The steering device 100 is a device capable of independently steering a plurality of steered wheels 200 . In the case of this embodiment, the steering device 100 steers the steered wheels 200 via, for example, a suspension mechanism. FIG. 1 exemplifies a strut-type suspension mechanism, which is one of suspension mechanisms, and a steering device 100 is interposed between the strut-type suspension mechanism and a vehicle body 210 such as a tire housing. , the shock absorber 220 and the spring 240 turn around the strut shaft 230 to steer the steerable wheels 200 . The strut-type suspension mechanism further includes a knuckle 250 attached to the steerable wheel 200, a lower arm 260 connected to the lower portion of the knuckle 250, and a joint member that connects each part so as to be jointable.

FIG. 2 is a cross-sectional view showing the internal structure of the steering system. As shown in the figure, the steering device 100 includes a motor 110 , a speed reducer 120 and a brake 150 . In the case of this embodiment, the steering device 100 includes a first rotation sensor 141 , a second rotation sensor 142 and a brake control section 181 .

The motor 110 is a driving source that generates a driving force for turning the steerable wheels 200 . In the case of this embodiment, motor 110 is a servomotor that includes rotary shaft 111 , rotor 112 , magnet 113 , and coil 114 .

The rotary shaft 111 is a rod-shaped rigid body that outputs the rotational driving force of the motor 110 . The rotary shaft 111 is a member elongated relative to the lengths of the rotor 112, the magnets 113, and the coils 114 in the axial direction (the Z-axis direction in the figure). Specifically, the rotary shaft 111 passes through the central portion of the wave generator 121 and the brake 150 from the vicinity of the output side member 171 connected to the external gear 124 (described later) of the speed reducer 120 . In the case of this embodiment, the rotary shaft 111 has a tubular shape with a hollow portion 115 penetrating therethrough in the axial direction.

The rotor 112 is a member that transmits torque generated between the magnet 113 and the coil 114 to the rotating shaft body 111 . The shape of the rotor 112 is not particularly limited, but in the case of the present embodiment, a short cylindrical holding portion 116 that holds the magnet 113 and the holding portion 116 and the outer peripheral surface of the rotary shaft 111 are connected to each other. A connecting portion 117 is provided. The holding portion 116 is arranged coaxially with the rotary shaft 111 , and the connecting portion 117 is integrally attached to one axial end portion of the holding portion 116 . The rotor 112 has a vessel shape, and at least part of a brake 150 for stopping the rotating shaft body 111 is accommodated inside the rotor 112 . Thereby, the axial length of the steering device 100 can be suppressed.

The magnets 113 are members that generate torque for rotating the rotating shaft body 111 by interacting with the magnetic force generated by the coils 114, and are attached to the outer peripheral surface of the holding portion 116 of the rotor 112 side by side in the circumferential direction. The magnets 113 are arranged side by side so that the directions of the north and south poles are in a predetermined pattern.

The coil 114 is a member wound with a conductive wire that constitutes an electromagnet that generates a magnetic field that acts on the magnet 113 . The winding axis direction of the coil 114 is along the radial direction centering on the axis of the rotating shaft body 111 . The coils 114 are arranged slightly outside the area where the magnet 113 rotates, and are arranged side by side in the circumferential direction so as to surround the magnet 113 . Coil 114 is fixed to the inner peripheral surface of cylindrical housing 160 . Note that the coil 114 may have a core that concentrates the magnetic field.

The speed reducer 120 is a device that is connected to the rotating shaft 111 of the motor 110 and amplifies the rotational torque generated by the motor 110 to a rotational torque that can steer the steered wheels 200 . Although the type of speed reducer 120 is not particularly limited, in the case of the present embodiment, a wave motion speed reducer having an input shaft and an output shaft coaxial is employed as speed reducer 120 . This wave motion reducer has a cylindrical internal gear 123 made of a rigid body, a cylindrical external gear 124 having external teeth meshing with the internal teeth of the internal gear 123 and having flexibility in the radial direction, An elliptical wave generator 121 is provided that deforms an external gear 124 into an elliptical shape with respect to an internal gear 123 and meshes with the internal gear 123 at a plurality of locations, and rotates the meshing positions along the internal gear 123 .

In the case of this embodiment, the external gear 124 is a so-called silk hat type, and includes a cylindrical portion 125 having external teeth formed at one end and a flange portion protruding radially outward at the other end of the cylindrical portion 125. 126. The flange portion 126 is arranged on the input side with respect to the external teeth. An outer peripheral end of the flange portion 126 is fixed to a housing 160 to which the coil 114 is fixed. By arranging the external gear 124 in this state, a cross roller bearing that rotatably fixes the internal gear 123 to the housing 160 outside the cylindrical portion 125 between the external teeth and the flange portion 126. A first bearing 127 such as a first bearing 127 can be arranged, and a portion of the brake 150 or the like can be arranged inside the cylindrical portion 125 . Therefore, it is possible to reduce the length of the steering device 100 in the axial direction.

The wave generator 121 is coaxially attached to the rotating shaft 111 in a penetrating state, and a rotational torque is directly input from the rotating shaft 111 . Further, the rotation axis of the wave generator 121 is determined by the rotating shaft body 111 .

The internal gear 123 is rotatably fixed to the housing 160 to which the coil 114 is fixed via the first bearing 127, and functions as a member on the output side. An output side member 171 is fixed to the internal gear 123 so as to cover the output side. A universal joint 172 is attached to the output side member 171 . The internal gear 123 is connected to the strut shaft 230 of the suspension mechanism via the output side member 171 and the universal joint 172 and outputs rotational torque for steering the steerable wheels 200 .

Brake 150 is a device that suppresses transmission of torque between motor 110 and speed reducer 120 . Specifically, the brake 150 can suppress and stop the rotation of the rotary shaft 111, which is the output shaft of the motor 110, by friction. In the case of the present embodiment, the brake 150 is a non-energized brake that can apply the brake when not energized and release the brake when energized. Specifically, the brake 150 is an excitation type brake whose operation is controlled by an electromagnet 155 (see FIG. 3) and an urging member (not shown). , and operating means 154 .

The brake disc 151 is a member that is fixedly attached to the rotary shaft 111 and is an annular member that protrudes in the radial direction of the rotary shaft 111 and has a rectangular cross section. The brake disc 151 is a member that rotates together with the rotary shaft 111 and is sandwiched between the brake pad 152 and the armature 153 to generate torque in a direction opposite to the rotation of the rotary shaft 111 by friction.

The brake pad 152 is a member arranged on the opposite side of the operating means 154 with respect to the brake disc 151 and fixed to the operating means 154 . The brake pad 152 is an annular member having a rectangular cross section that extends in the radial direction of the rotating shaft 111 and is arranged to surround the rotating shaft 111 , and is arranged parallel to the brake disc 151 .

The armature 153 is arranged on the opposite side of the brake pad 152 with respect to the brake disc 151, and is moved in a direction to sandwich the brake disc 151 together with the brake pad 152 by the biasing force of the biasing member provided in the operating means 154. When the provided electromagnet 155 is excited, it is a member that moves in a direction approaching the operating means 154 against the biasing force of the biasing member. The armature 153 is an annular member having a rectangular cross section that extends in the radial direction of the rotating shaft 111 and is arranged to surround the rotating shaft 111 , and is arranged parallel to the brake disc 151 .

The operating means 154 is a cylindrical member fixed to the housing 160 and includes a biasing member for reciprocating the armature 153 in the axial direction of the rotary shaft 111 and an electromagnet 155 . The biasing member is, for example, a coil spring, and the operating means 154 includes a plurality of coil springs arranged in the circumferential direction.

The first rotation sensor 141 is a sensor that detects the rotation angle on the output side of the speed reducer 120 . Although the type of the first rotation sensor 141 is not particularly limited, an optical rotary encoder can be exemplified. In the case of this embodiment, the first rotation sensor 141 has a detection shaft 143 . One end of the detection shaft 143 passes through the wave generator 121 of the reduction gear 120 and is connected to the rotation center of the output side member 171 on the output side of the reduction gear 120 . Further, the detection shaft 143 is inserted through the hollow portion 115 of the rotary shaft 111 , and the other end of the detection shaft 143 protrudes from the rotary shaft 111 . The first rotation sensor 141 detects the rotation angle of a disk portion 144 provided at the other end of the rotating shaft 111 , and detects the rotation angle of the speed reducer 120 on the input side of the speed reducer 120 and on the opposite side of the speed reducer 120 to the motor 110 . The rotation angle of the output side of the speed reducer 120 is detected based on the rotation of the detection shaft 143 on the side. Note that the first rotation sensor 141 is arranged farther from the speed reducer 120 than the brake 150 and the second rotation sensor 142 are.

As described above, by arranging the first rotation sensor 141 at a position farther from the speed reducer 120 than the motor 110 using the detection shaft 143, a plurality of rotation sensors can be gathered at one place, and the rotation sensor can be It is possible to facilitate dustproof measures and the like. In addition, output signals from a plurality of rotation sensors can be concentrated in one place and led out of the housing 160, so that signal lines outside the housing 160 can be routed easily. It is to be noted that the wire for power supply to the motor 110, the power wire for supplying the brake 150, and the like are concentrated in the same position as the signal wire and led out of the housing 160, so that the wiring can be further facilitated. . A connector (not shown) passing through the housing 160 facilitates connection and disconnection with electric wires outside the housing 160, and dust prevention can also be achieved.

The second rotation sensor 142 is a sensor that is attached to the rotating shaft body 111 of the motor 110 and detects the rotation angle of the motor 110 . Although the type of the second rotation sensor 142 is not particularly limited, a resolver is employed in this embodiment. The resolver can accurately sense the rotation angle of the rotating shaft 111 rotating at high speed.

As described above, by acquiring the rotation angle on the output side with the first rotation sensor 141 and acquiring the rotation angle on the input side with the second rotation sensor 142, the second rotation angle is detected with respect to the information based on the first rotation sensor 141. If the information from the sensor 142 is not in the predetermined relationship, the information from the first rotation sensor 141 can be used to calibrate the second rotation sensor.

The housing 160 is a box-shaped member that accommodates the motor 110, the brake 150, at least the input side of the speed reducer 120, the second rotation sensor 142, and the first rotation sensor 141 in the listed order. The shape of the housing 160 is not particularly limited, but in the case of the present embodiment, it is cylindrical, and the vicinity of the first rotation sensor 141 is closed by the lid member 161 . The housing 160 forms a so-called tire house in which at least the input side of the motor 110, the brake 150, and the speed reducer 120, the second rotation sensor 142, and the first rotation sensor 141 accommodate the steered wheels 200 and the suspension mechanism. It is fixed to the vehicle body 210 so as to be arranged outside the portion 210 . In the case of this embodiment, the housing 160 also accommodates an internal gear 123 on the output side of the reduction gear 120 and a part of the output side member 171, and the internal gear 123 is located outside the vehicle body 210. are placed in Although the housing 160 is attached so as to protrude outward from the vehicle body 210, it is not visible to the outside because it is covered by the bonnet of the vehicle.

As described above, in the steering device 100 according to the present embodiment, the brake 150 is interposed and connected between the motor 110 and the speed reducer 120 . It can resist torque or moment of inertia, and can prevent damage to the steering device 100 due to occurrence of a reverse input.

In addition, since the torque is suppressed against the rotational torque of the motor 110 before it is amplified by the speed reducer 120 or the moment of inertia, the torque generated by friction can be set small. Therefore, a compact brake 150 can be employed, and the steering device 100 can be miniaturized, particularly thinned in the axial direction.

A rotation angle sensor is provided on the output side of the speed reducer 120 by sensing the rotation angle on the output side of the speed reducer 120 using the detection shaft 143 with the first rotation sensor 141 arranged at the position on the input side. The axial length of the steering device 100 can be made shorter than in the case.

In addition, the motor 110, the brake, the speed reducer 120, the first rotation sensor 141, and the second rotation sensor 142 are arranged above the vehicle body 210 that partitions the tire housing where the steered wheels 200 are arranged, and attached to the vehicle body 210. Since it is housed in the housing 160, high dustproof performance can be obtained.

In addition, since electric wires for exchanging electric signals and electric power between the inside and outside of the housing 160 can be collected in one place, it is possible to easily handle harnesses.

In addition, by adopting a de-energized brake, when power is not supplied to the steering device 100 such as when the vehicle is stopped, the brake 150 fixes the rotating shaft body 111 and the steered wheels 200 can be moved. It becomes possible to regulate steering.

When the brake control unit 181 determines that the behavior of the steered wheels 200 is abnormal based on the information from the first rotation sensor 141 , the brake control unit 181 operates the brake 150 to generate torque against the rotation of the rotary shaft 111 . Here, the state in which the steered wheels 200 behave abnormally is, for example, a case where the steered wheels 200 contact a curb while the vehicle is running and the steered wheels 200 turn in an unintended direction.

FIG. 3 is a block diagram showing functions of the brake control unit. As shown in the figure, the brake control unit 181 is part of a steering ECU (Electronic Control Unit) 180, and includes a rotation angle acquisition unit 182, a timer unit 183, an angular velocity calculation unit 184, and an abnormality determination unit 185. , an electromagnet control unit 186 , and a vehicle state acquisition unit 187 .

The rotation angle acquisition unit 182 is a processing unit that acquires the rotation angle from the first rotation sensor 141 . Specifically, the rotation angle acquisition unit 182 may simply count the pulse signals from the first rotation sensor 141, or may calculate the rotation angle from the number of pulses.

The clock unit 183 is a processing unit that measures time. The timing method of the timing unit 183 is not particularly limited, but the time may be measured based on the sampling period of the brake control unit 181, for example. For example, one sampling period may be time 1. Alternatively, the actual time may be calculated by multiplying the number of sampling cycles by the sampling cycle.

The angular velocity calculation unit 184 calculates angular velocity based on the rotation angle obtained from the rotation angle acquisition unit 182 and the time obtained from the clock unit 183 . Specifically, for example, the angular velocity calculator 184 may use the difference in rotation angle for one sampling period of the brake controller 181 as the number of pulses obtained from the first rotation sensor 141 and acquire this value as the angular velocity. Also in this case, it is assumed that the rotation angle is divided by the time obtained from the timer 183 .

When the angular velocity obtained from the angular velocity calculator 184 is greater than or equal to a predetermined angular velocity threshold, the abnormality determination section 185 estimates that reverse input has occurred and determines that there is an abnormality.

Electromagnet control unit 186 controls electromagnet 155 provided in brake 150 to apply brake torque to rotary shaft 111 when abnormality determination unit 185 outputs a signal indicating an abnormality. In the case of the present embodiment, brake 150 is of the non-excitation type, so electromagnet control unit 186 applies brake torque to rotary shaft 111 by cutting off the power supply to electromagnet 155 .

As described above, the inertia torque of the motor 110 can be suppressed by applying a brake to the rotary shaft 111 when a reverse input occurs. Therefore, it is possible to prevent the reduction gear 120 from being damaged by the reverse input from the output side and the inertia torque from the input side.

The vehicle state acquisition unit 187 acquires the state of the vehicle to which the steered wheels 200 are attached, for example, whether the vehicle is running or stopped from a higher-level ECU such as a steering ECU, and controls the brake 150 according to the state of the vehicle. . In the case of the present embodiment, vehicle state acquisition unit 187 outputs a signal to electromagnet control unit 186 to cut off power supply to electromagnet 155 when acquiring information that the vehicle is parked. As a result, it is possible to prevent the steered wheels 200 from turning even when the vehicle is rear-ended while the vehicle is stopped.

It should be noted that the present invention is not limited to the above embodiments. For example, another embodiment realized by arbitrarily combining the constituent elements described in this specification or omitting some of the constituent elements may be an embodiment of the present invention. The present invention also includes modifications obtained by making various modifications to the above-described embodiment within the scope of the gist of the present invention, that is, the meaning of the words described in the claims, which a person skilled in the art can think of. be

For example, the steering device 100 according to the above embodiment has been described as a device that steers the steered wheels 200 via a suspension mechanism such as the shock absorber 220 and the strut shaft 230. 100 may steer the steerable wheels 200, or the steerable wheels 200 may be steered via a steering mechanism separate from the suspension mechanism.

In addition, although the strain wave gear mechanism was exemplified as the speed reducer 120 in which the input shaft and the output shaft are arranged coaxially, the speed reducer 120 is not limited to this, and for example, a speed reducer 120 using a planetary gear mechanism, etc. But it doesn't matter.

Moreover, the steering device 100 may be provided with an overload protection device 130 as shown in FIG. The overload protection device 130 is a so-called torque limiter that cuts off torque transmission between the motor 110 and the speed reducer 120 when an overload occurs. The overload protection device 130 includes a first member 131 arranged coaxially with the rotary shaft 111 and fixed to the outer peripheral surface of the rotary shaft 111 , and a through hole 128 of the wave generator 121 on the input side of the speed reducer 120 . A second member 132 attached to the outer peripheral edge of the second member 132, a biasing member 133 biasing the second member 132 against the first member 131, and interposed between the first member 131 and the second member 132 and a spherical engaging member 134 that is disposed and strongly engages the first member 131 and the second member 132 when the second member 132 is pressed against the first member 131 by the biasing member 133. .

Normally, in the overload protection device 130, the first member 131 and the second member 132 are strongly coupled via the engaging member 134 by the biasing force of the biasing member 133, so that the rotation of the rotating shaft body 111 is prevented. Torque is transmitted to the wave generator 121 of the speed reducer 120 . On the other hand, when a sudden reverse input occurs due to the steered wheels 200 striking a curb, etc., when the rotational torque of the reverse input weakened by the reduction gear 120 from the strut shaft 230 overcomes the biasing force of the biasing member 133. , the second member 132 idles with respect to the first member 131, and the reverse input does not reach the first member 131, the rotating shaft body 111, and the like.

Since the overload protection device 130 is arranged on the input side of the speed reducer 120 , it operates against reverse input rotational torque reduced by the speed reducer 120 . That is, it is possible to reduce the threshold value of the rotational torque when the overload protection device 130 idles, and the compact overload protection device 130 can be employed. Therefore, it becomes possible to suppress the size of the steering device 100 as a whole.

Also, as shown in FIG. 4 , the brake 150 may be arranged on the opposite side of the speed reducer 120 with respect to the motor 110 . The brake 150 protects the reduction gear 120 by suppressing the inertia torque of the motor 110 before the overload protection device 130 idles. In addition, the brake 150 reduces the number of idle rotations of the overload protection device 130 and can protect the overload protection device 130 .

Also, part or all of the steering device 100 may be arranged inside the tire house.

INDUSTRIAL APPLICABILITY The present invention can be used for vehicles such as automobiles, construction machinery, agricultural machinery, etc., in which steerable wheels are steered independently.

DESCRIPTION OF SYMBOLS 100... Steering apparatus, 110... Motor, 111... Rotating shaft, 112... Rotor, 113... Magnet, 114... Coil, 115... Hollow part, 116... Holding part, 117... Connection part, 120... Reduction gear, 121... Wave generator 123 Internal gear 124 External gear 125 Cylindrical portion 126 Flange 127 First bearing 128 Through hole 130 Overload protection device 131 First member 132... Second member 133... Biasing member 134... Engaging member 141... First rotation sensor 142... Second rotation sensor 143... Detection shaft 144... Disc portion 150... Brake 151... Brake Disk 152 Brake pad 153 Armature 154 Operating means 155 Electromagnet 160 Case 161 Lid member 171 Output side member 172 Universal joint 181 Brake control section 182 Rotation Angular acquisition unit 183 Time measurement unit 184 Angular velocity calculation unit 185 Abnormality determination unit 186 Electromagnet control unit 187 Vehicle state acquisition unit 200 Turning wheel 210 Vehicle body 220 Shock absorber 230 Strut shaft 240 Spring 250 Knuckle 260 Lower arm

Claims (4)

a motor that generates driving force for independently steering the steered wheels;
a speed reducer connected to the rotary shaft of the motor;
a brake that suppresses transmission of torque between the motor and the speed reducer;
a first rotation sensor that detects the rotation angle of the output side of the speed reducer;
a brake control unit that operates the brake when the behavior of the steered wheels is abnormal based on information from the first rotation sensor;
A steering device. The brake control unit
a timer that measures time;
an abnormality determination unit that determines an abnormality in the behavior of the steered wheels based on the rotation angle obtained from the first rotation sensor and the angular velocity calculated from the measured time;
The steering device according to claim 1, wherein the brake is operated when the abnormality determination section determines that there is an abnormality. The brake control unit
3. The steering apparatus according to claim 1 , wherein the brake is operated when the vehicle to which the steered wheels are attached is stopped. The brake
The steering device according to any one of claims 1 to 3 , which is of a non-energization operation type that stops rotation of the rotary shaft of the motor by friction when power is not supplied.

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